Centerless grinder



Oct. 29, 1963 D. c. HUGHES 3,103,407

CENTERLESS GRINDER Filed April 24. 1961 5 Sheets-Sheet l 111 iq-1INVENTOR DANIEL C.HU6HES ATT NEY Oct. 29, 1963 D. c. HUGHES CENTERLESSGRINDER 5 Sheets-Sheet 2 Filed April 24. 1961 mlfillml.

Oct. 29, 1963 D. c. HUGHES 3,103,407

CENTERLESS GRINDER Filed April 24. 1961 5 Sheets-Sheet 5 TIP 11.5

1IF" oAmil'Y'EY'B enEs B( 44140 1 RNEY Oct. 29, 1963 D. c. HUGHESCENTERLESS GRINDER 5 Sheets-Sheet 4 Filed April 24, 1961 DANIE EfINVENTOR' L C. H GHES A NEY Oct. 29, 1963 D. c. HUGHES 3,108,407

CENTERLESS GRINDER Filed April 24, 1961 5 Sheets-Sheet 5 INVENTOR '5 QDANIEL C.HUGl-IES E I at: l J FL 1 M 44/ n j v 44/ m g E 3 25 c: ATV NEYUnited States Patent Grinders, Inc, Riverdale, Ni, a corporation of NewJersey Filed Apr. 24, N61, Ser. No. 104,929 11 Claims. (Cl. 51-103) Thepresent invention relates to abrading or grinding machines, and, moreparticularly, to centerless grinders of the plunge-feed type havingimproved mechanism for feeding the work and controlling the grindingthereof.

The present invention is primarily concerned with, but not restricted toplunge-feed centerless grinders for rapidly producing one or morerelatively small parts which are generally circular in cross-section.Such machines generally comprise a work wheel or grinding wheel andregulating or feeding wheel for receiving the Work therebetween, a workrest for supporting the work between the wheels, a slidably mounted ramon which the regulatmg wheel is mounted, and plunge-feed mechanism forreciprocating the ram to move the regulatory wheel there on towards andaway from the work wheel. Since numerout parts of various shapes andsizes are to be produced on such machines, it is necessary to adjust thespeed of movement and the dwell time of the ram having the regulatingwheel thereon in order to properly feed, grind and release the work.

'Heretofore, grinding machines of this general type have been proposedbut never met with the commercial success expected thereof because theplunge-feed mechanism was unduly complicated, because they did notprovide for the aforementioned adjustments, and because they failed totake into account other considerations involved where a machine wasrequired to produce a large variety of parts.

Accordingly, an object of the present invention is to provide acenterless grinder of the plunge-feed type which is not subject to theforegoing difficulties and disadvantages.

Another object is to provide such a grinder having an extremely simpleand sturdy plunge feed mechanism.

Another object is to provide such a plunge-feed mechanism which can beadjusted very accurately to predetermine the speed and the length of thestroke of the ram and its dwell time in both its inner and outerpositions.

Another object is to provide such a plunge-feed mechanism which can beoperated through a single cycle while the machine is being adjusted forgrinding a particular part and can be switched over for repeated cyclingand mass production after such adjustments have been made.

Another object is to provide such plunge-feed mechanism which can beinstalled on grinders already in the field or newly manufacturedgrinders.

A further object is to accomplish the foregoing in a practical, reliableand economical manner.

Other and further objects of the invention will be obvious upon anunderstanding of the illustrative embodiment about to be described, orwill be indicated in the appended claims, and various advantages notreferred to herein will occur to one skilled in the art upon employmentof the invention in practice.

A preferred embodiment of the invention has been chosen for purposes ofillustration and description, and is shown in the accompanying drawings,forming a part of the specification, wherein:

FIG. 1 is a more or less schematic plan view of a centerless grinder inaccordance with the present invention illustrating the relationship ofthe Work wheel, the work rest, the regulating wheel, the ram and theplunge-feed mechanism.

anism as seen from the front of the grinder.

ice

FIG. 3 is a sectional view taken along the line 3-3 on FIG. 2illustrating the driving connection between the ram and the plunge-feedmechanism.

FIG. 4 is a sectional view taken along the line 4--4 on FIG. 3illustrating additional details of the driving connection.

FIG. 5 is a diagrammatic sectional view of a speed control device for afluid pressure operated motor which drives the plunge-feed mechanism.

FIG. 6 is a wiring diagram of the electrical control network for themotor.

Referring now to FIG. 1 of the drawings in detail, there is shown acenterless grinder which generally comprises a base or stand 10 having aplatform 11 on the top thereof, a work wheel 12 mounted on andjournalled for rotation at the back of the platform, a longitudinalslide 14 on the platform at the intermediate portion thereof, a ram 15slidably mounted for movement on the slide, a regulating wheel 16mounted and journal-led for rotation on the ram and facing the workwheel, a work rest 17 between the wheels and adjacent the Work wheel forinitially supporting the work with its axis of rotation just above aplane passing through the axes of rotation of the wheels in theconventional manner, and plunge-feed mechanism 18 for reciprocating theram in the manner as described hereinafter at the front of the platform.

Conventional drive mechanism (not shown) is provided for effectingrotation of the work wheel 12 and the regulating wheel 16 which includesa motor and gearing adapted to be mounted within the base or stand 10.Also, conventional automatic work feeding mechanisms (not shown) may beprovided for delivering the work to the work rest 17 or the work may befed manually to the wheels.

As shown in FIGS. 2, 3 and 4, the plunge-feed mechanism 18 and itsdriving connection for reciprocating the ram 15 generally comprises afluid pressure operated motor 19, such as a reversible air motoroperable by factory air at about p.s.i., a cross-slide 20 for a gearrack 21 which is driven by the motor 19, an annular member such as aspur gear 22 in mesh with the rack and journalled for rotation in afixed position to prevent movement longitudinally with respect to theplatform 11, the gear 22 having a screw threadedcentral opening 24, ashaft 25 having one end secured to the ram 15 and provided with a screwthreaded portion 26, and a screw sleeve 23 threaded through the opening24 and about the portion 26.

The cross-slide 20 comprises a sleeve section 27 slidably mounted bybushings 28 on a fixed rod 29 mounted at its ends on the platform, acarriage section 30' having the gear rack 21 at the underside thereofand having a pair of upper and lower spaced rollers 31 at each end, anda rail 32 parallel to the rod 29 and mounted on the platform and havinga horizontal flange 34 engaged at the top and bottom by the rollers 31.

The spur gear 22 is journalled for rotation in a block 35 by a bearing36, and the outer end of the shaft 25 is slidably mounted in a bushing37 in the block 35. The outer end of the gear 21 has a handwheel 38thereon (FIG. '1) for effecting manual movement of the ram 15 whilesetting up the machine to determine the end points of movement of theregulating wheels.

The gear teeth of the rack 21 and the gear 22 and the threads of theopening 24- and the screw sleeve 23 preferably are ratioed to effectmovement of the ram back and forth about three eighths of an inch uponmovement of the cross-slide back and forth about six inches, whereby asmall adjustment in the length of the stroke or the speed of travel ofthe cross-slide can be accurately made to provide an extremely fineadjustment for the stroke of the ram.

The screw sleeve 23 is prevented from turning with the gear 22 by a key61 which is removably secured to the plunge feed mechanism framestructure in a fixed position and extends into a longitudinal siot 62 inthe sleeve 23 (FIG. 3) so that sleeve 23 is reciprocated and moves theshaft 25 therewith by reason of the screw threaded connection thereto.The ram has an end wall 63 formed with an opening 64 for receiving theshaft and the shaft has a shoulder 65 thereon for engaging one side ofthe wall 63 to feed the ram towards the left as viewed, and the innerend of the shaft has a collar 66 screw threaded thereon and removablysecured thereto by a pin 67 for engaging the other side of the wall 63to retract the ram towards the right as viewed.

As the work wheel and/ or regulating wheel wear down and are reduced indiameter, the end points of movement of the ram must be readjusted toenable the regulating Wheel to properly engage the work. This isaccomplished by loosening the collar 66 to free the shaft 25 forturning, turning the shaft by means of the hand wheel 38 to move theshaft by reason of its screw threaded connection in the sleeve 23towards the left as viewed, and then securing the collar on the shaft toagain secure the shaft to the ram.

As shown in FIG. 2, the length of the cross-slide stroke and the extentof movement in the direction to withdraw or retract the ram is adjustedby a member '75 slidably mounted for adjustment lengthwise on thecross-slide 26 at the rear end thereof for operating a ram advancingswitch described hereinafter. By extending this member further outwardlythan shown and securing it in its adjusted position by a screw 43, thereturn stroke of the air motor and the ram is shortened and the advancestroke commences again much sooner. For example, the normal returnstroke of six inches can be shortened to two inches in cases where rapidautomatic operation is desired.

The air motor 19 comprises a cylinder 3? mounted in fixed position abovethe cross-slide 20 and provided with conventional connections andvalving for reversible operation of the motor, a slidable piston 40 inthe cylinder, and a piston rod 41 extending outwardly of the cylinderand connected to a yoke 42 on the cross-slide.

The air motor 19 is adapted to effect rapid movement of the cross-slide20 and the ram 15 in either direction, but as already indicated,provision is made for slowing down the speed of travel of thecross-slide in its direction to move the regulating wheel intoengagement with the Work. This is accomplished by a hydraulic fluidcheck 44 operatively connected to the cross-slide and mounted above theair motor cylinder 39.

The check 44, as shown in FIGS. 2 and 5, generally comprises a cylinder45 having an opening 46 at one end and an opening 47 at its other end, aslidable piston 48 in the cylinder, a rod 49 connected to the piston andextending outwardly at one end above the air motor piston rod 41, ahydraulic fluid by-pass or transfer tube 50 conmeeting the openings 4-6and 47, and an expansion chamber 51 acting as a reservoir for the fluidconnected to the opening 47.

The check 44 and the air motor piston rod 41 are operatively connectedby a stop 52 mounted near the free end of the rod 49 for lengthwiseadjustment thereon, and an arm 54- secured at its lower end to the yoke42 of the cross-slide 2t} and having a lug 55 at its upper end formedwith an aperture 56 through which the rod 49 extends, so that thecross-slide moves freely until the lug 55 engages the stop '52. As thisoccurs, the piston 48 which has hydraulic fluid at both sides thereofslows down the movement of the cross-slide and the inward movement ofthe ram 15. The point at which such slow down takes place during theoutward movement piston rod 41 is determined by the position of the stop'52 on 4 the rod 49. The rate of slow down can be adjusted by a needlevalve 56 in the transfer tube 50.

The rod 49 and the piston 48 thereon are returned or moved inwardlywhere the lug 55 engages a stop 53 secured to the rod 49- near the endof the cylinder from which rod extends when the piston is at theopposite end of the cylinder.

The chamber 51 comprises a cylinder 57, a slidable piston 58 in thecylinder, an opening 59 in the cylinder at one side of the pistonconnected to the opening 47 and a spring 60 in the cylinder at the otherside of the piston. In this manner the expansion chamber acts as areservoir for the volume of fiuid displaced by the piston 4-8 on itsinward stroke (to the right as viewed), and returns this amount to thecylinder 45 on the outward stroke (to the left as viewed), whereby thecheck 44 does not slow down the cross-slide 2t) and the ram 15 duringthe return stroke.

In FIG. 6, a wiring diagram of the electrical control network for theair motor is shown which includes manually and automatically operatedswitches certain of which are also shown in FIG. 2, and a timer 70 forcontrolling the response of electrical components to the switch. Such atimer may be of the adjustable electronic type such as a Bellows ModelEDT 1 Timer which for the purpose of understanding the present inventionneed not be illustratecl or described in detail.

More particularly, this network includes a manually operable startingswitch 71 for causing the regulating wheel to be advanced towards thework wheel, a manually operable switch 72 for causing the regulatingwheel to be retracted, an automatic advancing switch 73 and an automaticretracting switch 74 both under the control of the air motor operatedcross-slide 20 (this being accomplished by the adjustable member '75 onthe cross-slide 2t) and a projection 76 on the arm 54 for respectivelyengaging these switches at the end of the retracting and advancingstrokes (FIG. 2), a switch 77 for connecting the switches 73 and 74 inthe network for automatic cycling, and a solenoid 78 arrangement underthe control of the switches 71, 72, 73 and 74 for controlling thevalving (not shown) of the air motor to effect reciprocation thereof.

The timer 70 has terminals T1 to T10 to which the switches and the relayare connected, as about to be described, and has terminals T and T forconnecting a source of electrical power.

The switches 71, 72 and 77 are of the single pole single throw type andeach have two terminals. One terminal of the switch 71 is connected toline All and its other terminal is connected to line A4; one terminal ofthe switch 72 is connected to line A1 and its other terminal isconnected to line A3 and line A53; one terminal of the switch '77 isconnected to line A9 and line A89 and its other terminal is connected toline A2.

The switches 74 and 73 comprise a pair of single polo double throwswitches 79 and 8t} and 81 and 82, respectively, each have threeterminals with the pairs of switches being operable by members 83 and84, respectively, connected to the switch arms but insulated therefromand controlled by the projection 76 and the member 75, respectively.

Only two of the terminals of the switch 79 are utilized and these areconnected to lines A53 and A89, respectively. The terminals of theswitch are respectively connected to lines A10, A8 and A6. The terminalsof the switch 81 are respectively connected to A5, A8 and A10. Only twoof the terminals of the switch 32 are utilized and these are connectedto lines A2 and A4, respectively.

The solenoid valve operating arrangement has three terminals which arerespectively connected to lines S3, S7 and S4.

The lines prefixed A (automatic) and S (solenoid) are connected toterminals T of the timer of like number. The lines AS3 and A89 merelyare connections for automatic switching and are connected to the timerterminals by the lines A3 and A9. In view of this wiring identificationsystem, it is not necessary to describe the path and connections of eachline in greater detail. Certain of the common connections are made atthe switch terminals as already indicated, and others are made through aterminal block 35. i

In operation, the stop 52 and the member 75 are adjusted to determinethe point at which the air motor is slowed down by the check 44 and thepoint at which the return stroke is terminated, respectively. The workwheel 12 and regulating wheel 16 are operated at the desired speed, awork piece is fed to these wheels, and operation of the plunge-feedmechanism L5 is controlled manually to test the machine for properadjustment. After properly adjusting the machine by further adjustmentof the handwheel 38, the stop 52 and the member 75, if required, themachine can be set for automatic repeated cycle operation.

The air motor .19 is operated manually to advance the ram by clasing theswitch 71, which through the timer energizes the lines S4 and S7 andcauses the solenoid arrangement to open a valve for admitting air at theright end of the cylinder 3-9 and move the piston 40, its rod 41 and thecross-slide 20 in the direction to advance the ram. At the end of thisstroke the switch 71 is opened and the switch 72 is closed whereby linesS3 and S7 are energized through the timer to cause the soienoidarrangement to open a valve for admitting air at the left end of thecylinder 39 and move the piston 40-, its rod 41 and the crossslide in anopposite direction to retract the ram.

When the machine is to be operated automatically the switches 71 and 72are open and the switch 77 is closed. Assuming that the air motoroperated cross-slide 20 is in its retracted position (to the right asviewed, FIG. 2), the member 75 has moved the switch arms respectivelyconnected to iines A3 and A2 of the switches 31 and 82 into engagementwith contacts in lines Ali and A4. Lines A8 and Alt} control anelectronic time delay device for the lines A2 and A4 (84 wherebyoperation of the air motor in the ram advancing direction is delayed. Asthe cross-slide 20 is moved towards the left as viewed, it is sloweddown by the check 44, and at the end of this stroke, the projection 76moves the switch arms respectively connected to lines A59 (A9) and A8 ofthe switches '75 and 86 into engagement with contacts in lines A83 (A3)and A10. Lines A8 and Ale again control the electronic time delay devicebut for the lines A3 (S3) and A9 whereby operation of the air motor inthe ram retracting position is delayed :to permit dwell of theregulating wheel for spark out of the ground work.

When lines A5 and A8 are connected by the switch 81, the time delaydevice is switched to affect the lines A3 (S3) and A9; and when thelines A6 and A8 are connected by the switch 8%, the time delay device isswitched to affeet the lines A2 and A4 (S4), whereby a single time delaydevice controls the delay of the retracting and advancing strokes.

From the foregoing description, it will be seen that the presentinvention provides an improved plunge-feed control mechanism which hasmany advantageous features and is simple and economical in construction,has a minimum of mechanical parts, and is accurate and reliable inoperation.

As various changes may be made in the form, construction and arrangementof the parts herein, without departing from the spirit and scope of theinvention and with out sacrificing any of its advantages, it is to beunderstood that all matter herein is to be interpreted as illustrativeand not in any limiting sense.

I claim:

1. In a centerless grinder, the combination of a work wheel and aregulating wheel for receiving the work to be ground therebetween, aslidably mounted ram having said regulating wheel mounted thereon at oneend and having a horizontal longitudinally extending screw threadedshaft at its opposite end, a normally fixed block facing the lastmentioned end of said ram, annular means journalled for rotation in afixed position on said block, said block having central screw threadedmeans for cooperation with the threads of said shaft and having gearteeth on the periphery thereof, a cross-slide on said block, an elongategear rack on said cross-slide having teeth in engagement with said gearteeth of said annular means for effect ing rotation of said annularmeans to move saidram longitudinally upon crosswise movement of saidcross-slide, power operated means having a stroke for directly effectingblack and forth movement of said cross-slide through a relatively longstroke, said screw threaded means and said screw threads on said shafthaving a pitch for eifecting back and forth movement of said ram througha relatively short stroke whereby the ratio of the cross-slide stroke tothe ram stroke is such that a small adjustment of the length of thestroke and speed of travel of said cross-slide can be accurately made toprovide a fine adjustment of the stroke of said ram, a cross-slidemounting arrangement which comprises bushing means and i3. pair ofrollers on said cross-slide, a rod on said block extending through saidbushing means in sliding engagement therewith, and a rail on said blockextending between said pairs of rollers and engaged thereby, [wherebysaid crossslide is maintained in a straight path to impart an evenstroke to said ram.

2. In a centerless grinder, the combination of a work wheel and aregulating wheel for receiving the work to be round therebetween, aslidably mounted ram having said regulating wheel mounted thereon at oneend and having a horizontal longitudinally extending screw threadedshaft at its opposite end, a normally fixed block facing the lastmentioned end of said ram, annular means journalled for rotation in afixed position on said block, said block having central screw threadedmeans for cooperation with the threads of said shaft and having gearteeth on the periphery thereof, a cross-slide on said block, an elongategear rack on said cross-slide having teeth in engagement with said gearteeth of said annular means for eifecting rotation of said annular meansto move said ram longitudinally upon crosswise movement of saidcross-slide, power operated means having a stroke for directly effectingback and forth movement of said cross-slide through a relatively longstroke, said screw threaded means and said screw threads on said shafthaving a pitch for effecting back and tooth movement of said ram througha relatively short stroke whereby the ratio of the cross-slide stroke tothe ram stroke is such that a small adjustment of the length of thestroke and speed of travel of said cross-slide can be accurately made toprovide a fine adjustment of the st oke of said ram, a hydraulic checkcomprising a cylinder having its longitudinal axis parallel to thestroke of said cross-slide, a piston in said cylinder and i8. rodsecured to said piston and extending outwardly of said cylinder, a stopadjacent the outer end of said rod, means on said cross-slide positionedfor free movement lengthwise with respect to said rod and for engagingsaid stop near the end of the stroke of said cross-slide effectinginfeed movement of said ram to slow down said cross-slide, whereby saidregulating wheel on said ram initially moves rapidly towards said workwheel and said regulating wheel moves slower upon engagement of saidstop by said cross-slide means, a switch on said block for controllingsaid power operated means to stop infecd movement of said cross-slideand to initiate return movement of said cross-slide, and an element onsaid crossslide for actuating s aid switch near the end of the infeedstroke of said cross-slide.

3. A grinder according to claim 2, wherein the length of the stroke ofsaid cross-slide is at least about ten times as great as the length ofthe stroke of said ram.

4. A grinder according to claim 2, wherein said stop and said rodinclude means for adjustably positioning said stop on said rod todetermine the point at which said cross-slide is slowed down.

5. A grinder according to claim 2, wherein timing means control saidswitch for causing said ram to dwell at the end of its infeed stroke.

6. A grinder according to claim 2, wherein said rod has a second stopthereon engageable by said cross-slide means only near the end of itsreturn stroke to reposition said rod.

7. A grinder according to claim 6, wherein said second stop and said rodinclude means for adjustably positioning said stop on said rod.

8. A grinder according to claim 2, including a second switch forcontrolling said power operated means to stop return movement of saidcross-slide and to initiate infeed movement of said cross-slide, andmeans on said crossslide for actuating second switch near the end of thereturn stroke of said cross-slide.

9. A grinder according to claim 8, wherein timing means control saidsecond switch for causing said crossslide to dwell at the end of itsreturn stroke.

10. In a centerless grinder, the combination of a work wheel and aregulating wheel for receiving the work to be ground therebetween, aslidably mounted ram having said regulating wheel mounted thereon at oneend and having a horizontal longitudinally extending screw threadedshaft at its opposite end, a normally fixed block facing the lastmentioned end of said ram, annular means journalled for rotation in afixed position on said block, said block having central screw threadedmeans for cooperation with the threads of said shaft and having gearteeth on the eriphery thereof, a cross-slide on said block, an elongategear rack on said cross-slide having teeth in engagement with said gearteeth of said annular means for efiecting rotation of said annular meansto move said ram longitudinally upon crosswise movement of saidcross-slide, power operated means having a stroke for directly effectingback and forth movement of said cross-slide through a relatively longstroke, said screw threaded means and said screw threads on said shafthaving a pitch for effecting back and forth movement of said ram througha relatively short stroke whereby the ratio of the cross-slide stroke tothe ram stroke is such that a small adjustment of the length of thestroke and speed of travel of said cross-slide can be accurately made toprovide a fine adjustment of the stroke of said ram, said annular meansincluding a sleeve slid'ably mounted in said block having internalthreads cooperating with the threads of said shaft and having externalthreads, and a gear providing said gear teeth and having an internalthreaded bore for cooperating with said external threads of said sleeve,manually operable means connected to said shaft for effecting rotationand longitudinal movement of said shaft within said sleeve to adjust theposition of said ram, means for releasably securing said shaft to saidram to normally prevent rotation of said shaft, and means for releasablysecuring said sleeve to said block to prevent rotation of said sleevewith respect to said gear.

11. In a grinder according to claim 10, including means for adjustingthe length of the stroke of said power operated means to therebydirectly adjust the length of the stroke of said cross-slide andproportionally adjust the length of the stroke of said ram.

References ited in the tile of this patent UNITED STATES PATENTS2,042,257 Harrison et al May 26, 1936 2,756,546 Barhorst July 31, 19562,921,414 Garberding Jan. 19, 1960 2,963,832 Ohringer Dec. 13, 1960

1. IN A CENTERLESS GRINDER, THE COMBINATION OF A WORK WHEEL AND AREGULATING WHEEL FOR RECEIVING THE WORK TO BE GROUND THEREBETWEEN, ASLIDABLY MOUNTED RAM HAVING SAID REGULATING WHEEL MOUNTED THEREON AT ONEEND AND HAVING A HORIZONTAL LONGITUDINALLY EXTENDING SCREW THREADEDSHAFT AT ITS OPPOSITE END, A NORMALLY FIXED BLOCK FACING THE LASTMENTIONED END OF SAID RAM, ANNULAR MEANS JOURNALLED FOR ROTATION IN AFIXED POSITION ON SAID BLOCK, SAID BLOCK HAVING CENTRAL SCREW THREADEDMEANS FOR COOPERATION WITH THE THREADS OF SAID SHAFT AND HAVING GEARTEETH ON THE PERIPHERY THEREOF, A CROSS-SLIDE ON SAID BLOCK, AN ELONGATEGEAR RACK ON SAID CROSS-SLIDE HAVING TEETH IN ENGAGEMENT WITH SAID GEARTEETH OF SAID ANNULAR MEANS FOR EFFECTING ROTATION OF SAID ANNULAR MEANSTO MOVE SAID RAM LONGITUDINALLY UPON CROSSWISE MOVEMENT OF SAIDCROSS-SLIDE, POWER OPERATED MEANS HAVING A STROKE FOR DIRECTLY EFFECTINGBACK AND FORTH MOVEMENT OF SAID CROSS-SLIDE THROUGH A RELATIVELY LONGSTROKE, SAID SCREW THREADED MEANS AND SAID SCREW THREADS ON SAID SHAFTHAVING A PITCH OF EFFECTING BACK AND FORTH MOVEMENT OF SAID RAM THROUGHA RELATIVELY SHORT STROKE WHEREBY THE RATIO OF THE CROSS-SLIDE STROKE TOTHE RAM STROKE IS SUCH THAT A SMALL ADJUSTMENT OF THE LENGTH OF THESTROKE AND SPEED OF TRAVEL OF SAID CROSS-SLIDE CAN BE ACCURATELY MADE TOPROVIDE A FINE ADJUSTMENT OF THE STROKE OF SAID RAM, A CROSS-SLIDEMOUNTING ARRANGEMENT WHICH COMPRISES BUSHING MENS AND A PAIR OF ROLLERSON SAID CROSS-SLIDE, A ROD ON SAID BLOCK EXTENDING THROUGH SAID BUSHINGMEANS IN SLIDING ENGAGEMENT THEREWITH, AND A RAIL ON SAID BLOCKEXTENDING BETWEEN SAID PAIRS OF ROLLERS AND ENGAGED THEREBY, WHEREBYSAID CROSSSLIDE IS MAINTAINED IN A STRAIGHT PATH TO IMPART AN EVENSTROKE TO SAID RAM.